The discussion of the background of the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge at the priority date of any of the claims.
Light radiation according to their spectral range (UV, visible, IR) can be harmful and/or uncomfortable for the wearer of an optical equipment comprising optical lenses mounted in a spectacle frame.
Among the radiation that may arrive to the eye of the wearer or to the skin in a peri-orbital zone of the wearer one may consider the following type of radiation.
First, transmitted radiation entering through the front face of the optical lens and transmitted up to the eye. Such radiation arrive to the eye either directly by two refractions or by a more complex path with internal reflections on the rear face of the optical lens and then on the front face of the optical lens before being finally refracted by the rear face of the optical lens and reach the eye of the wearer.
Secondly, the reflected radiation that arrive to the eye after having been reflected by the rear face of the optical lens. Typically the radiation arriving from behind the wearer may if they are not subjected to a shadowing effect of the head of the wearer or of the spectacle frame, be reflected by the rear face of the optical lens towards the eye of the wearer.
Thirdly, direct radiation that arrive directly to the eye of the wearer without been reflected or transmitted by the optical lens.
Generally, optical lenses effectively absorb harmful UV radiation that could be transmitted directly through the lens and transmit useful visible radiation. But radiation arriving from behind the wearer may be reflected by the multilayer coating applied to the rear face of the lens and therefore reach the eye of the wearer. Standard multilayer coatings are designed so as to reduce the amount of uncomfortable visible radiation being reflected.
Specific coatings that reduces the reflection of UV radiation may be applied on the back surface of the optical lens so as to limit the dangerous radiation that reach the eye of the wearer after having been reflected on the rear surface of the optical lens.
However, many other parameters than the coating of the rear surface of the optical lens may influence the quantity of indirect radiation reaching the eye of the wearer. For example the shape of the spectacle frame and/or the morphology of the face of the wearer and/or the geometry of the optical lens may influence the amount of indirect radiation reaching the eye of the wearer. The geometry of the optical lens may also influence the number of direct radiation reaching the eye of the wearer after having passed through the optical lens.